And those who strictly guard their Salawat.
means, they persistently offer their prayers at their appointed times,
Ibn Mas`ud said;
"I asked the Messenger of Allah, `O Messenger of Allah, which deed is most beloved to Allah!'
He said,
الصَّلَةُ عَلَى وَقْتِهَا
Prayer at the appointed time.
I said, `Then what!'
He said,
بِرُّ الْوَالِدَيْن
Kindness to one's parents.
I said, `Then what!'
He said,
الْجِهَادُ فِي سَبِيلِ الله
Jihad in the way of Allah.
It was recorded in the Two Sahihs.
Qatadah said;
"At the fixed times, with the proper bowing and prostration."
Allah begins and ends this list of praiseworthy qualities with Salah, which is indicative of its virtue, as the Prophet said;
اسْتَقِيمُوا وَلَنْ تُحْصُوا وَاعْلَمُوا أَنَّ خَيْرَ أَعْمَالِكُمُ الصَّلَةُ وَلَا يُحَافِظُ عَلَى الْوُضُوءِ إِلاَّ مُوْمِن
Adhere to righteousness, you will never be able encompass it all. Know that the best of your deeds is Salah. None will preserve his Wuddu' except the believer.
Having described them with these praiseworthy characteristics and righteous deeds, Allah then says;
أُوْلَيِكَ هُمُ الْوَارِثُونَ